1. Field of the Invention
The present invention relates to an AC generator driven by an internal combustion engine and, particularly, a vehicular AC generator that can be equipped on a vehicle such as a passenger car, a truck, or a ship.
2. Description of the Related Art
Recently, output power of AC generators has been increased to meet increase in electric loads such as safety control apparatus.
A structure for a powerful vehicular AC generator is well known, as disclosed in International Publication Number WO 92/06527 (1992). In the above-described conventional structure, it is proposed that U-shaped conductor members are inserted into plural slots of a stator core from the same direction and edge portions thereof are connected with each other after circumferentially bending to form a stator winding. In this structure, a higher slot-space factor of conductor members can be achieved by inserting regularly U-shaped conductor members, thereby to obtain higher output power.
In the above-described structure, however, conductor members are disposed close to each other at coil ends and clearances therebetween are small due to a high slot-space factor thereof. Therefore, conductor members may collide with each other at vehicular vibration or the like, thereby to damage insulation coating thereof. Conductors members also might be in contact with each other at damaged portions of insulation coating, thereby, causing an electric short-circuit.
In the above-described structure, because radial clearances between conductor members are small, centrifugal cooling-air, which includes circumferential cooling-air generated by an inner fan, cannot easily pass through the radial clearances therebetween in a circumferential direction. Therefore, it is difficult to improve cooling efficiency.
A main object of the present invention is to provide a stator which can solve the above problems and ensure reliable insulation between conductor members at coil ends.
Another object of the present invention is to provide a stator having an improved stator winding of a high cooling efficiency.
According to an aspect of the present invention, clearances are formed between conductor members at coil ends of the stator winding.
Therefore, collisions between conductor members under vehicle vibrations or the likes can be reduced. Accordingly, insulation films of conductor members are not damaged by the collisions. Furthermore, cooling air can easily pass through the radial clearances provided between conductor members in a circumferential direction, thereby improving cooling efficiency.
According to another aspect of the present invention, the clearance between the conductor members at the coil ends is larger than a clearance between the conductor members in the slots.
Because conductor members disposed in the same slot form a stator winding having the same electrical phase, electric power generation is not affected by a short circuit due to contact between conductor members in the same slot. On the other hand, because stator windings having different electrical phases different from each other are located adjacent to each other at the coil end, electric power generation is affected by a short circuit due to contact between conductor members. However, because the clearance between conductor members radially adjacent to each other is larger at the coil end than in a slot, the collisions can be reduced, so that reliable insulation between conductor members can be ensured.
According to another feature of the present invention, one conductor member is bent in an arc shape, thereby forming a clearance between the other conductor member radially adjacent thereto and one conductor member.
In this structure, it is easy to form a clearance between one conductor member and the radially adjacent another conductor member by bending one of them in arc shape.
According to another feature of the present invention, the radial width of a portion of the conductor members is reduced by forming concave portions at coil ends.
Because of the concave portions, conductor members, insulation between the conductor members can be ensured and cooling capacity of coil ends can be improved.
According to another feature of the present invention, the conductor members have the connection portions at the coil ends. They have step portions respectively formed to be thicker in the radial direction. Two conductor members can be disposed radially in close to each other near the connection portions. On the other hand, a plurality of conductor members can be separated from each other at a distance from the connection portions.
According to another feature of the present invention, a manufacturing process of a vehicular AC generator""s stator includes a step of inserting plural conductor members in plural radial layers in each slot, a step of bending straight portions away from the straight portions of the other conductor members radially adjacent thereto, and a step of forming clearances between the conductor members. The step of forming clearances includes a step of bending the same straight portions of the one conductor members in opposite directions.
If the conductor members are bent, they are hardened mechanically at the bent portions. Therefore, even if once-bent conductor members are again bent at the once-bent portions in the opposite direction, the bent portions cannot restore the original straight shapes. If the straight portions of conductor members at radially opposite end layers in each slots are bent in a direction away from straight portions of conductor members radially adjacent thereto, they are hardened mechanically at the bent portions of the straight portions. Therefore, when the straight portions of conductor-members are again bent in an opposite direction to be brought near the straight portions of conductor members radially adjacent thereto, they are bent at the bent portions hardened mechanically. Therefore, the straight portions of conductor members cannot be restored to the original straight shapes and curve to form clearances between conductor members radially adjacent to each other from the bent portions to edge portions. Accordingly, clearances can be provided between conductor members radially adjacent to each other.